Centralized traffic controlling system for railroads



R. M. PHINNEY GENTRALIZED TRAFFIC CONTROLLING SYSTEM FOR RAILROADS Filed May 29, 1937 mtozuu UL t. 26 ibubm SOL ENE INVENTOR ouc G c0530 Em m .vmpumccou ATTORNEY Patented May 9, 1939 PATENT OFFiCE CENTRALIZED TRAFFIC CONTROLLING SYSTEM FOR RAILROADS Robert M, Phinney, Rochester, N. Y., assignor to General Railway Signal Company, Rochester,

Application May 29,

9 Claims.

This invention relates to the communication part of a coded centralized traific controlling system for railroads, and it more particularly pertains to a means for selectively sectionalizlng the communication line circuits at the various field locations of such a system.

In certain selector or coded types of communication systems for centralized trafiic controlling systems, one or more line circuits connect a control office with the various outlying field stations. It Will be obvious that the complete system may be thrown out of operation by trouble in the line circuits, such as a broken line'wire.

In view of the above and other considerations, it is proposed in accordance with this invention to provide a means for automatically sectionalizing the line circuit of a coded or multiple impulse centralized trafiic controlling system at that particular one of the several stations which will render that portion of the system operative up to that particular station in spite of line trouble further away from the control office. It is further proposed to provide in this sectionalizing means, an automatic restoring means for again returning the series line circuit to its normal condition after such a trouble condition has been corrected, which restoring means is supplemented by a manually operable restoring means.

Other objects, purposes and characteristic features of the invention will appear as the description thereof progresses, during which reference will be made to the accompanying single sheet of drawing, which diagrammatically shows a sufiicient portion or" a centralized traific controlling system, to illustrate the manner of sectionalizing the line in accordance with the present invention.

The drawing has been shown in a manner to make it easily understood, rather than with the idea of showing a particular or complete arrangement employed in practice. Therefore, certain conventional illustrations have been employed and the relays and their contacts have been illustrated in a conventional manner with symbols to indicate the connection of their terminals to suitable batteries, or other sources of electric current, instead of showing all of the wiring connections to these terminals.

The symbols and are employed to indicate the positive and negative terminals respectively of suitable batteries, or other sources of direct current; and the circuits with which these symbols are used always have current flowing in the same direction. However, if it should be desired to use alternating current, then these 1937, Serial No. 145,542

symbols may be considered to represent the relative instantaneous values.

Fig. 1 of the accompanying drawing shows the present invention applied to the line circuit ar-' rangement of the prior patent to T. J. Judge et a1. Patent No. 2,082,544, dated June 1, 1937. It is to be understood, however, that the present invention may be employed with any type of coded communication system and is not limited to the one shown in the above-mentioned prior application, but this particular prior system has been chosen as the type of system to which the present invention has been applied for the sake of simplifying the present disclosure.

The line circuit arrangement includes a control line wire l0 extending from the central oflice through the field stations with a common return line wire [2, and also includes an indication line wire I4 extending from the central office through the several field stations with an indication return line wire it. The indication line wires are open ended at the last field station, while the control line wires are connected together at the last field station.

A system of this type is employed to send controls to a plurality of field stations connected to the control line circuit, of which one is diagrammatically indicated to the right of the vertical dashed line. A control office is indicated to the left of this vertical dashed line and it will be understood that two way transmission may be effected between the office and the station by transmitting controls over the control line circuit and by transmitting indications over the indication line circuit. The transmission of controls is accomplished by transmitting dilferent series of positive and negative impulses from a control battery CB in the control office over the line wires Ill and I2; while the transmission of indications is by the opening and closing of the indication line circuit including line wires l4 and IE to selectively allow energy to flow from the indication battery IB. This selective opening and closing of the indication line circuit is provided on each impulse period and each time space period marked off during a series of impulses on the control line circuit.

The line wire l0 includes a neutral relay F at the control office and a three-position polar relay F (with suitable exponent) at each field station which repeats the impulses of each series of impulses impressed upon the control line circuit. The particular polarity of the impulses of each series placed upon the control and stepping line circuit is determined by polarity selecting 55 relays PC and NC which determine respectively whether the impulses are positive or negative in character. The duration of each impulse of a series as well as the time spaces between such impulses is determined in accordance with the operation of an impulsing relay EP described in detail in the prior Patent No. 2,082,544.

At the control oifice, each impulse is repeated by the relay F irrespective of its polarity and repeating relays PP and 2F? are provided to repeat the relay F in succession. A slow acting relay SA isprovided for marking off the different series of impulses by being picked up at the beginning of each different series and by dropping at the end of each diiferent series. This is accomplished by providing that the relay SA is slow in picldng up upon the application of the first impulse of each series but is relatively much slower in dropping away so as to maintain its front contacts closed during the time spaces between impulses in each series of impulses. The relay SA is also provided with a repeater relay BSA which is controlled through front contact I0 of relay SA by an obvious circuit. The circuits for the relays FF and ZFP have not been shown inasmuch as such repeating operation has been shown in detail in the prior Patent No. 2,082,544.

Similar relays are provided at each of the field stations, but for convenience, only the relays F FF and SA have been shown at one field station which is assumed to be typical of all of the field stations of the system.

The indication line circuit comprising the line wires IQ and I6 is energized from an indication battery IB, as above mentioned, and has included therein at the control oflice, message receiving relays MF and MB Which are respectively controlled through front and back contacts I15, I76 and 206 of relays FF and ZFP, as well as through front and back contacts I5! of a dividing relay DV controlled by the impulsing relay EP. Back contact I58 of relay ZSA also serves to control the relay MB for initiating the system from the field stations.

The indication line wire I4 extends to all of the field stations and normally includes a back contact, such as back contact I56 of the lockout relay L0 at each of the field stations, as well as including a back contact, such as back contact HE! of the sectionalizing relay SECS at each of those field stations provided with the sectionalizing equipment arranged in accordance with the present invention.

When a particular field station is transmitting, the lockout relay LO (with suitable exponent) at that station is picked up to render the indication line circuit dependent upon the transmitting relays PF and PB (not shown) merely indicated by xxx in the drawing for the sake of simplicity.

A sectionalizing relay SEC is provided in the control oiiice to energize the sectionalizing repeating relay SECP, under certain conditions more specifically pointed out hereinafter, to cause the sectionalization of the line. The relay SECP is slow to pick up for reasons pointed out hereinafter, but is preferably relatively quick in dropping.

A selecting relay SEL is provided at each of the field stations, and is of the high resistance type so that when it receives energy from the control line circuit it does not pick up if such energy is of the potential supplied by the control battery CB, but is capable of picking up when a somewhat higher potential is supplied to the control line by the booster battery BB in the central ofiice. It is to be understood that the difference in potential between the batteries BB and CB is chosen in accordance with the usual engineering requirements to provide the proper margins of operation between the line relays F and selecting relays SEL.

It is also to be understood that the particular circuit arrangement employed may have substituted therefor circuit arrangements to provide that the booster battery BB is connected in series with the control battery CB at such times that it is desired to cause the sectionalization of the system and still be within the scope of the present invention.

In this connection, it should be noted that these batteries CB, BB and IB may have substituted therefor other sources of electric potential such as alternating current and in such an event the voltage applied through front contacts of the slow pick-up relay SECP is of a sufficiently high potential to pick up the relays SEL but the potential supplied in place of the battery CB will not pick up such relays SEL although it will readily operate the control line relays F.

Sectionalizing stick relay SECS is provided at each field station to which the present invention is applied, being picked up after a time interval following the picking up of relay SEL this time interval being measured by thermal relay THR Fig. 2 is a schematic illustration of three thermal relays THR THR and THR assumed to be located at the first, second and third stations from the control office, these relays having different pick up times as indicated by the legends below the relays. These relays are provided with different pick up times for the purpose of holding off the operation of sectionalizing stick relays at stations nearer the office, when a particular station is to sectionalize the line. In other words, a break in the line circuit may occur just beyond station No. 3, which will be effective to operate the SEL relays at the first three stations, so that it becomes necessary to permit the station farthest from the control office to sectionalize the line and remove the selecting relays at the other stations, before the sectionalizing equipment at lhese other stations function.

General operation.-Under normal conditions, the line circuits are deenergized and the communication system is at rest. Upon the initiation of the system from either the control office or a field station by the actuation of a starting button (not shown) or by the dropping of a change relay at the field station (not shown), a series of impulses of the distinctive polarities is placed upon the stepping and control line circuit to comprise a cycle of operation. The characters of these impulses are determined in accordance with the code jumpers and control levers for a cycle of operation initiated from the control ofiice. The relay PC or the relay NC is picked up for each step of a step-by-step mechanism in accordance with the position of the code jumper or control lever allotted to that step. In other words, a stepping relay bank is employed at the control oflice and at each field station to take one step for each time space period marked off on the stepping and control line circuit.

For a cycle of operation for the transmission of indications alone, the impulses placed upon the stepping line circuit are all of one character, so that one of the polarity determining relays PC or NC is picked up at the beginning of a cycle and is maintained picked up until the end of that cycle. During such a cycle of operation, the impulses placed upon the stepping and control line circuit are merely for the purpose of causing the operation of the stepping relay banks at the control ofiice and at the field stations.

At the beginning of a cycle of operation, disregarding the type of cycle, one of the polarity determining relays PC or NC is picked up thereby placing an impulse upon the stepping line circuit, This is repeated by the line relays F at the control ofiice and at each of the field stations as well as by their respective line repeating relays. After this impulse has been applied for a prede- 'termined period of time suificient for picking up the slow acting relays SA and their repeater relays, the stepping circuit is opened by the contact 52 of the relay EP. When a suficient period of time has elapsed for the time space following the first impulse, the backcontact 52 of relay EP is again closed. In brief then, the contacts 50, 5|, 53 and 54 of the relays PC and NC act as pole changing contacts so that particular polarities are placed upon the step-ping line circuit from the control battery CB; while the back contact 52 of relay EP is intermittently operated to space the impulses of a cycle of operation. It may be stated in this connection, that the relays PC and NC assume their positions while the back contact 52 of relay EP is open, but. remain in static or steady conditions during the time that the back contact 52 is closed.

As previously mentioned, the relay FF and its repeating relay 2FP at the control office repeats each energization of the line circuit irrespective of its polarity. Similarly, each energization of the line circuit is repeated by the relay FP at the field station through an obvious circuit including polar contact IOI of the relay F After the first impulse of a cycle the relay DV is subject to the relay EP. In other words, each time the relay EP is deenergized to cause an impulse, the relay DV is energized and picks up.

Assuming that the relay L is picked up at the field station to condition that station for transmission of indications, then during each time space in the series of impulses the positive terminal of the indication battery IB is connected to the line wire! through the lower winding of the relay MB and the indication circuit is dependent for its closed or open conductive condition upon the contact of a particular code sending relay.

More specifically, the relay MB has a circuit closed including the indication battery 13, back contact I51, back contact 206, back contact I16, front contact I56 and the contacts of the code sending relay.

Similarly, during each impulse placed upon the stepping line circuit, the indication. line circuit is dependent for its open or closed conductive condition upon another code sending relay which conditions the message receiving relay MF through a circuit including the indication battery IB and front contacts I51, I15, I16 and I56.

In other words, during the time space of each series of impulses, the message receiving relay MB is controlled in accordance with the open or closed condition of the indication line circuit, while during the impulses of each series the message receiving relay MP is controlled in accordance with the open or closed condition of the indication line.

At the end of a cycle of operation, the impulsing relay EP is picked up and opens the stepping and control line circuit at back contact 52 for a sufiicientlylong time to allow the deenergization of all of the cycle demarking relays SA and their repeaters.

Sectionalizatz'on of system-It will now be considered that a trouble condition exists beyond the first field station, assumed to be the illustrated field station by reason of the distinctive exponents used in connection with the apparatus shown in Fig. 1. Such a trouble condition may be a broken wire, so that it becomes necessary to close up the line at station No. l for providing a continuous circuit for control and stepping impulses.

As disclosed in the above mentioned Judge et al. patent, the control ofiice initiates the system into operation, either in response to a manual start in the control office or in response to an automatic start initiated over the indication line circuit from the field station. Such initiation results in the picking up of the PC or NO relay for energizing the line circuit. Under the present assumption, the line is not complete, due to the trouble condition, and therefore relay F is not picked up. A circuit is now closed for picking up relay SEC which extends from front contact I30 of relay PC (or front contact I40 of relay NC), winding of relay SEC, back contact I 50 of relay F and back contact I60 of relay SA, to

Relay SECP is energized over an obvious circuit closed at front contact I! of relay SEC and after a short time interval (provided to make sure that relay SECP does not pick upduring normal operation of the system), relay SECP picks up and the line circuit is energized over a circuit extending from the terminal of battery BB, front contact I8 of relay SECP, line conductor I2, winding of relay SEL back contact I02 of relay SA back contact I03 of relay FP line conductor I0, winding of relay F, back contact 52 of relay EP and front contact I9 of relay SECP to the terminal of battery BB. This comparatively high voltage effects the picking up of relay SEL It will be understood that relay SEL does not pick up when the line is first energized from battery CB. Also, in the event that there are other stations in towards the office, the SEL relays at these stations. pick up when battery BB is connected to the line.

A circuit is now closed for the heating element of thermal relay THR at front contact IM of relay SE-L and after a measured time interval, relay THR closes its contact I05 for picking up relay SECSV Relay SECS is stuck up over a circuit extending from normally closed contact I05 of release button BB back contact I01 of code release relay CRL front contact I08 and winding of relay SECS to The closure of front contactl09 of relay SECS closes up the line circuit and the centralized trafiic controlling system may now be operated to control the apparatus at the field station, inasmuch as the line circuit is now completed as far as this station.

The energization of the line circuit, in response to the closure of front contact I09, effects the picking up of relay FP which in turn removes relay SEL from the bridging of the line by reason of back contact I03. Relay SA maintains the circuit of relay SEL open through the following cycle at back contact I02. Similar operations are effective at any other station orstations nearer the control ofiice.

In the control office, the picking up of relay F releases relay SEC because of open back contact I5 and relay SECP releases because of open front contact H, to disconnect battery BB from the line and to extent the line to the pole changer contacts of the PC and NC relays and thence to the regular line battery CB.

It is to be understood that the response of the line relay F after the sectionalizing contact at a field station, such as contact I09 at the first field station, closes the control line circuit, is sufiiciently quick to cause the relays SEC and SECP to drop away and remove the booster battery BB from the control line circuit before the cycle deniarking relays SA and their repeaters can be picked up. Thus the closure of back contacts 18 and E9 of the relay SECP connects the control battery CB and a cycle of operation is initiated the same as if the control line were not sectionalized. It might be pointed out in this connection that the line relays F do not pick up while the booster battery BB is connected to the control line circuit even though there are several of the selecting relays SEL at the field stations connected in multiple across the control line. In other words, the total amount of current drawn from the booster battery BB by the selector relays SEL in multiple is insufficient to cause the line relays F to pick up.

It should also be understood that the picking up of the sectionalizing relay SECS opens back contact I It in the indication line circuit so that the indication line wire terminates at this first field station so far as the transmission of indications is concerned. One of the reasons why this opening or" the indication line Wire i l is desirable may be readily appreciated, when it is considered that any one of the field stations more remote from the control office may have start conditions registered at such field station and endeavor to cause the starting of the system by closing front contact I55 of its lockout relay LO (with suitable exponent), but inasmuch as the control line circuit is assumed to have been broken at some intervening point such station cannot transmit its indications. If the sectionalization of the indication line was omitted then the system would be initiated for successive cycles of operation and run substantially continuously; but with the sectionalization of the indication line as shown, then only the field stations which are capable of receiving control impulses for stepping purposes and the transmission of indications can cause the initiation of the system into operation.

When the broken line wire, or such trouble in the circuit as may have occurred, has been corrected, relay SECS may be restored to normal by opening its stick circuit by the operation of release button RB Or this stick circuit may be opened to release relay SECS by means of a manually selected code transmitted over the line circuit to this station for picking up relay CRL over a circuit selected by the step-by-step mechanism, in response to this code. It will be understood that the release of relay SEL opens the circuit of the thermal relay heating element, so that this element cools and restores the contact to its normal position.

In Fig. 2, it is assumed that the thermal relay at the third station has a one-second pick up time, the thermal relay at the second station has a two-second pick up time and the thermal relay at the first station has a three-second pick up time for the purpose above explained. It will be understood that these times may be varied from those indicated, to provide the required operation of the system, without departing from the spirit of the present invention.

A similar arrangement of relays and circuits may be associated with the other field stations, for sectionalizing the line circuit at a station at which, or beyond which, a trouble condition exists.

The present disclosure contemplates that a plurality of stations are employed with the system, such as station Nos. 1, 2 and 3 each of which is provided with a sectionalizing arrangement and organization such as shown in connection with the first station, and indicated in connection with the other stations in Fig. 2. However, it is to be understood that these sectionalizing organizations need be applied only at spaced intervals as required by the particular circumstances encoun tered in practice, and might be the station Nos. 3, 7 and 15, for example.

In other words, it is not necessary to have a sectionalizing arrangement at each of the several stations of a system. On the other hand, it might be desirable to provide the sectionalizing organization provided by the present invention at opposite ends of a particularly vulnerable portion of line circuit without the usual controlling device associated therewith.

The above rather specific description of one arrangement of the present invention is given solely by way of example and is not intended in any way whatsoever in a limiting sense. It is also to be understood that various modifications, adaptations and alterations may be applied to meet the requirements of practice without in any manner departing from the spirit or scope of the present invention as limited by the appended claims.

Having thus described my invention, what I claim is:

1. In a means for selectively sectionalizing a line connecting a control office with various field locations; means including a first source of current for energizing said line; a first relay connested in series with said line and a second relay connected in multiple with said line at one of said locations said second relay requiring a higher degree of energization for its operation than said first relay; a second source of current for supplying a higher potential than said first source; means for at times connecting said line to said first source of current; means effective if said line is not energized when said first source of current is connected thereto for connecting said second source of current thereto, whereby said second relay is operated; and means responsive to the operation of said second relay for sectionalizing said line at said one location.

2. In a means for selectively sectionalizing a normally deenergized line circuit connecting a control ofiice with a plurality of field stations; a line relay at the control office and at each of said field stations, all of said line relays being connected in series in said line circuit; impulsing means at the control office including a source of current for applying different series of current impulses to said line circuit; a sectionalizing relay connected in multiple across said line circuit at one of said field stations, said sectionalizing relay being unresponsive to said current impulses in said line circuit but being responsive to an energization of said line circuit with a relatively higher potential; means operating, if said impulsing means is ineffective to energize said line circuit with a series of impulses, to apply a relatively higher potential to said line circuit, whereby said sectionalizing relay is operated; and means Iii) controlled by the operation of said sectionalizing relay for shunting said line circuit at said one field station.

3. In a code type communication system having a control office and a plurality of field stations; a line relay at the control ofilce and at each of said field stations; a normally deenergized line circuit extending between the control oifice and the field stations and connecting all of said line relays in series; impulsing means at the control ofiice including a source of energy for applying different series of current impulses to said line; a sectionalizing relay connected in multiple across said line circuit at one of said field stations, said sectionalizing relay being unresponsive to the current impulses in said line circuit applied by said impulsing means but being responsive to an energization of said line circuit with a potential substantially higher than the potential supplied by said source of energy; means at said control office including another source of energy for acting, if said impulsing means is inefiective to cause current impulses in said line circuit after a predetermined time by reason of a break in said line circuit at a point more remote from said control office than said one field station, to apply a substantially higher potential to said line circuit, whereby said sectionalizing relay is operated; and means controlled by the operation of said sectionalizing relay for shunting said line circuit at said one field station to render said line relays controllable by said impulsing means at said control office.

4. In a code type communication system having a control office and a plurality of field stations; a line relay at the control office and at each of said field stations; a line circuit extending between the control ofiice and the field stations and connecting all of said line relays in series; impulsing means at the control ofiice including a source of energy for applying different series of current impulses to said line circuit; a high resistance relay connected in multiple across said line circuit at one of said field stations, said high resistance relay being unresponsive to the current impulses in said line circuit applied by said impulsing means but being responsive to an energization of said line circuit with a potential substantially higher than the potential supplied by said source of energy; auxiliary energizing means at said control ofiice including another source of energy for acting, if said impulsing means is inefiective to cause current impulses in said line circuit after a predetermined time by reason of a break in said line circuit at a point more remote from said control oifice than said one field station, to apply a substantially higher potential to said line circuit, whereby said high resistance relay is operated; means rendered efiective by the operation of said high resistance relay for shunting said line circuit at said one field station, whereby said line relays nearer the control office are energized; and means at the control ofiice responsive to the energization of said line relay in the control ofiice to cause said auxiliary energizing means to be rendered ineffective and said impulsing means to be rendered efiective to transmit impulses over the line circuit as sectionalized.

5. In a multiple impulse code type communication system connecting a control ofiice with a plurality of field stations; a line relay at the control office and at each of said field stations; a line circuit extending between the control oifice and the plurality of field stations for connecting all of said line relays in series; impulsing means at the control oflice for applying different series of current impulses to said line circuit; a high resistance line relay at a number of said field stations each being connected in multiple at its respective station across said line circuit, said I high resistance line relays being unresponsive to said current impulses provided by said impulsing means but being responsive to an increased energization of said line circuit; means operating, if said impulsing means is unable to energize .said line circuit with a series of impulses by reason of a break in said line circuit, to apply an increased potential to said line circuit, whereby certain of said high resistance line relays are operated; a timing device associated with each of said high resistance line relays, each of said timing devices requiring a different time for its operation with the longest time of operation being required by the device closest to the control oflice and with the times of operation for the remainline relay at its field station is energized; whereby 7 said line circuit is sectionalized at the field station nearest to the break having a high resistance relay on the control office side of such break in the line circuit.

6. In a means for selectively sectionalizing a first relay in series with said line circuit and a second, relay connected in multiple across said line circuit at said station, said second relay requiring a higher degree of energization for its operation than is required for said first relay; a source of control current; means for connecting said source of control current to said line circuit for energizing said line circuit and operating said first relay when and only when said line circuit is complete; auxiliary means effective to connect a booster source of current to said line if said first relay fails to operate when said control current is connected thereto, whereby said second relay is operated; means responsive to the operation of said second relay for sectionalizing said line circuit at said station; means responsive to said sectionalization of said line circuit for disconnecting said second relay from the line circuit; and other means acting on said auxiliary means for disconnecting said booster source of current from the line when said line circuit has been sectionalized.

'7. In a means for selectively sectionalizing a normally deenergized line circuit connecting a control office with a plurality of field stations; a line relay at the control offi'ce and at each of the field stations, all of said line relays being connected in series in said line circuit which is normally opened only at the control ofilce; impulsing means at the control office including a source of energy for applying different series of current impulses to said line circuit; auxiliary means effective to connect a booster source of current to said line circuit if said line circuit fails to be energized by said impulsing means, whereby the potential across said line circuit is substantially increased; sectionalizing relay means located at a particular one of said field stations and connected across said line circuit, said sectionaliz- 20 ing devices being respectively shorter for each' 85 line circuit at a station connected thereto; a

ing relay means being unresponsive to current impulses impressed on said line circuit by said impulsing means but being rendered active, in response to the increased energization of said line circuit by said auxiliary means, to shunt said line circuit until manually restored, whereby current will flow in said line circuit even though a break has occurred at a point more remote from the control ofiice than said particular field station; means at the control ofiice responsive to current fiow in said line circuit due to the increased energization of said line circuit for causing said auxiliary means to be rendered inefiective and said impulsing means to be rendered effective to transmit; and manually operable means located at said particular field station for restoring said sectionalizing relay means to a normal inactive condition.

8. In a means for selectively sectionalizing a normally deenergized line circuit connecting a control office with various field stations; a line relay included in series in said line circuit at the control office and at each of the field stations; a high resistance relay at several of said field stations, each being connected at its respective station across said line circuit, and each being unresponsive to current impulses of a normal potential for said line relay but being responsive to a relatively higher potential across said line circuit; impulsing means including a first source of current for applying different series of impulses of normal potential to said line circuit; auxiliary means at the control oflice for at times connecting a second source to apply a potential to said line circuit of said relatively higher value, said auxiliary means operating only if the control line relay at the control oflice fails to operate in response to the normal energization of said line circuit by said impulsing means; a timing device for each high resistance relay, each timing device being differently timed with the longest time of operation for the device closest to the control office and with the times of operation of the remaining devices being respectively shorter for each of the successive devices more remote from the control ofiice; means controlled by the operation of each of said high resistance relays for causing the operation of the associated timing device; sectionalizing means associated with each timing device and initially rendered active at the end of the time measured thereby to shunt said line circuit at its field station; means at the control ofiice responsive to the energization of said line relay in the control office to cause said auxiliary energizing means to be rendered inactive and said impulsing means to be rendered eifective to transmit impulses over the line circuit as sectionalized; and holding means for maintaining said sectionalizing means active to shunt said line circuit; whereby that one of said sectionalizing means nearest to a break in said line circuit on the control ofiice side of such break is effective to shunt said line circuit and render it available for use up to such station, and the sectionalizing means at the remaining stations nearer the control ofiice remain ineffective.

9. In a code type communication system for transmitting different series of impulses from a control office to any one of a plurality of field stations; a line relay at the control office and at each of the field stations; line wires extending between the control office and the several field stations for connecting all of said line relays in a series line circuit normally opened only at the control oifice; impulsing means at the control office for applying different series of current impulses to said line circuit from a source of energy; auxiliary energizing means at the control oifice governed by said line relay at the control oflice and operating, if said impulsing means is unable to energize said line circuit with a series of impulses by reason of a break in said line circuit, to apply an increased potential to said line circuit, sectionalizing means at one of said field stations rendered active only upon the increased energization of said line circuit and responsive to such increased energization irrespective of a break in said line circuit at a point more remote from the control office for shunting said line circuit on the remote side of the line relay at that station; holding circuit means acting on said sectionalizing means to maintain it active to shunt said line circuit until released; means at the control office responsive to the energization of said line relay in the control office upon current flow in said line circuit due to said increased potential to cause said auxiliary energizing means to be rendered ineffective and said impulsing means to be rendered effective; and means at said one field station responsive to a particular series of impulses for releasing said holding circuit means.

ROBERT M. PHINNEY. 

